2005-11-29 17:40:16 +00:00
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'\" t
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.\" Copyright (c) 2005 by Michael Kerrisk <mtk-manpages@gmx.net>
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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2006-07-12 13:33:46 +00:00
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.TH SIGSET 3 2005-12-01 "Linux 2.6.14" "Linux Programmer's Manual"
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2005-11-29 17:40:16 +00:00
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.SH NAME
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sigset, sighold, sigrelse, sigignore \- System V signal API
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.SH SYNOPSIS
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.B #define _XOPEN_SOURCE 500
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.br
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.B #include <signal.h>
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.sp
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.B typedef void (*sighandler_t)(int);
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.sp
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.BI "sighandler_t sigset(int " sig ", sighandler_t " disp );
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.sp
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.BI "int sighold(int " sig );
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.sp
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.BI "int sigrelse(int " sig );
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.sp
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.BI "int sigignore(int " sig );
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.SH DESCRIPTION
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These functions are provided in glibc as a compatibility interface
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for programs that make use of the historical System V signal API.
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This API is obsolete: new applications should use the POSIX signal API
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.RB ( sigaction (2),
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.BR sigprocmask (2),
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etc.)
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The
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.BR sigset ()
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function modifies the disposition of the signal
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.IR sig .
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The
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.I disp
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argument can be the address of a signal handler function,
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or one of the following constants:
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.TP
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.BR SIG_DFL
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Reset the disposition of
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.I sig
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to the default.
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.TP
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.BR SIG_IGN
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Ignore
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.IR sig .
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.TP
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.BR SIG_HOLD
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Add
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.I sig
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to the process's signal mask, but leave the disposition of
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.I sig
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unchanged.
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.PP
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If
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.I disp
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specifies the address of a signal handler, then
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.I sig
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is added to the process's signal mask during execution of the handler.
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.PP
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If
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.I disp
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was specified as a value other than
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2005-11-29 17:59:53 +00:00
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.BR SIG_HOLD ,
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then
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2005-11-29 17:40:16 +00:00
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.I sig
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is removed from the process's signal mask.
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.PP
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The dispositions for
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.B SIGKILL
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and
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.B SIGSTOP
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cannot be changed.
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.PP
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The
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.BR sighold ()
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function adds
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.I sig
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to the calling process's signal mask.
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The
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.BR sigrelse ()
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function removes
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.I sig
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from the calling process's signal mask.
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The
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.BR sigignore ()
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2006-07-20 13:53:47 +00:00
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function sets the disposition of
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2005-11-29 17:40:16 +00:00
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.I sig
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to
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.BR SIG_IGN .
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.SH RETURN VALUE
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On success,
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.BR sigset ()
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returns
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.B SIG_HOLD
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if
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.I sig
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was blocked before the call,
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or the signal's previous disposition
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if it was not blocked before the call.
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On error,
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.BR sigset ()
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returns \-1, with
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.I errno
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set to indicate the error.
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2006-02-10 18:46:42 +00:00
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.\" FIXME But as at 2.3.5, glibc's sigset() is broken for the
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.\" SIG_HOLD case: it will only return SIG_HOLD if 'disp' is
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.\" SIG_HOLD; if the signal is blocked, then sigset() should return
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.\" SIG_HOLD even if 'disp' is specified as something other than
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.\" SIG_HOLD (I have tested this on Solaris 8 and HP-UX 11).
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2005-11-29 17:40:16 +00:00
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.\" -- mtk, 29 Nov 05
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2005-11-30 13:33:11 +00:00
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.\" See http://sourceware.org/bugzilla/show_bug.cgi?id=1951
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2006-07-04 04:57:33 +00:00
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.\" 24 Apr 06: According to Ulrich Drepper the problem is now fixed.
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2006-07-04 04:53:00 +00:00
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.\" 4 Jul 06: Looking at the 20060626 glibc tree, the problem is fixed,
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.\" but the fix is not yet in a 2.4.x release.
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2005-11-29 17:59:53 +00:00
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2005-11-29 17:40:16 +00:00
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The
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.BR sighold (),
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.BR sigrelse (),
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and
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.BR sigignore ()
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functions return 0 on success; on error, these functions return \-1 and set
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.I errno
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to indicate the error.
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.SH ERRORS
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For
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.BR sigset ()
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see the ERRORS under
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.BR sigaction (2)
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and
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.BR sigprocmask (2).
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For
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.BR sighold ()
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and
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.BR sigrelse ()
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see the ERRORS under
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.BR sigprocmask (2).
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For
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.BR sigignore (),
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see the errors under
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.BR sigaction (2).
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.SH NOTES
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2005-11-30 13:33:11 +00:00
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These functions appeared in glibc version 2.1.
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2005-11-29 17:40:16 +00:00
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The
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.I sighandler_t
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type is a GNU extension; it is only used on this page to make the
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.BR sigset ()
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prototype more easily readable.
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The
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.BR sigset ()
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2005-11-29 17:59:53 +00:00
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function provides reliable signal handling semantics (as when calling
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2005-11-29 17:40:16 +00:00
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.BR sigaction ()
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with
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.I sa_mask
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2005-11-29 17:59:53 +00:00
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equal to 0).
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2005-11-29 17:40:16 +00:00
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On System V, the
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.BR signal ()
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2005-11-29 17:59:53 +00:00
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function provides unreliable semantics (as when calling
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2005-11-29 17:40:16 +00:00
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.BR sigaction ()
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with
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.I sa_mask
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equal to
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.IR "SA_RESETHAND | SA_NODEFER" ).
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On BSD,
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.BR signal ()
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provides reliable semantics.
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POSIX.1-2001 leaves these aspects of
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.BR signal ()
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unspecified.
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See
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.BR signal (2)
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for further details.
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In order to wait for a signal,
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BSD and System V both provided a function named
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.BR sigpause (),
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but this function has a different argument on the two systems.
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See
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.BR sigpause (3)
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for details.
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2005-11-30 13:33:11 +00:00
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.SH BUGS
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In versions of glibc before 2.2,
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.BR sigset ()
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did not unblock
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.I sig
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if
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.I disp
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was specified as a value other than
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.BR SIG_HOLD .
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In all versions of glibc up to and including 2.3.5,
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.BR sigset ()
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does not correctly return the previous disposition of the signal
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in two cases.
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First, if
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.I disp
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is specified as
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.BR SIG_HOLD ,
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then a successful
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.BR sigset ()
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always returns
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.BR SIG_HOLD .
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Instead, it should return the previous disposition of the signal
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(unless the signal was blocked, in which case
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.BR SIG_HOLD
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should be returned).
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Second, if the signal is currently blocked, then
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the return value of a successful
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.BR sigset ()
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should be
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.BR SIG_HOLD .
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Instead, the previous disposition of the signal is returned.
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2006-03-23 02:13:08 +00:00
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.\"FIXME This has been reported on 30 Nov 05 -- mtk
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2005-11-30 13:33:11 +00:00
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.\" See http://sourceware.org/bugzilla/show_bug.cgi?id=1951
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.\"
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2006-08-03 13:57:30 +00:00
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.\" The POSIX.1-2001 disposition of sigset() says:
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2006-02-10 18:46:42 +00:00
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.\" Upon successful completion, sigset() shall return
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.\" SIG_HOLD if the signal had been blocked and the signal's
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.\" previous disposition if it had not been blocked.
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.\" Otherwise, SIG_ERR shall be returned and errno set to
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.\" indicate the error.
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2005-11-29 17:40:16 +00:00
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.SH "CONFORMING TO"
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2006-08-03 13:57:30 +00:00
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SVr4, POSIX.1-2001.
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These functions are obsolete: do not use them in new programs.
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.SH "SEE ALSO"
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.BR kill (2),
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.BR pause (2),
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.BR sigaction (2),
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.BR signal (2),
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.BR sigprocmask (2),
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.BR raise (3),
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.BR sigpause (3),
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.BR sigvec (3),
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.BR signal (7)
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